Hi to all!
I recently bought a Mobile Keys 25 MIDI Keyboard.
When it first came out of the box I connected it to my iPhone 4 (iOS 7.1) and opened Alchemy Mobile Synth and it played fine. After that I installed MIDI Memo app to my phone and automatically this changed Mobile Keys' firmware.
After that it doesn't work. I keep having this message "this equipment is not compatible with this phone" or something like that. I contacted line 6 support & the guy I spoke with suggested that I should format my phone (re-install my iOS) and that should fix my problem. I did that but nothing changed.
How can I make my keyboard work with my phone? Please help!
Nikolas..

I finally resolved this issue and would like to share what I did in case it helps someone else.

My mobile keys 49 unit stopped working with any application after installing ios7 on my iPhone 4s. I checked to ensure that all of the compatible apps were up to date. Then I tested the keyboard on my computer using some desktop daws, and it worked fine. I stumbled upon the line6 monkey updater software and decided to download it to see if it would resolve my problem. It connected to the keyboard just fine, but didn't indicate that there were any updates available and didn't seem to do anything to the unit. After I disconnected from the computer, I plugged the keyboard into my phone and opened up the line6 midi recorder app. Lo and behold, it instantly told me there was a firmware update! It never lollipop did this before, so I assume that my connecting the unit to the monkey software triggered something. I have since tested the keyboard in my compatible iOS apps, and it works just fine.

Well, i've since updated my iPhone to ios8, and guess what? The keyboard is once again not recognized by any compatible app on my phone. I think this might actually be a more challenging issue than before, as most of my downloaded apps were barely functional after the OS update. I went through the same process that I did before, with no success.